4,668 research outputs found
From Type-II Triply Degenerate Nodal Points and Three-Band Nodal Rings to Type-II Dirac Points in Centrosymmetric Zirconium Oxide
Using first-principles calculations, we report that ZrO is a topological
material with the coexistence of three pairs of type-II triply degenerate nodal
points (TNPs) and three nodal rings (NRs), when spin-orbit coupling (SOC) is
ignored. Noticeably, the TNPs reside around Fermi energy with large linear
energy range along tilt direction (> 1 eV) and the NRs are formed by three
strongly entangled bands. Under symmetry-preserving strain, each NR would
evolve into four droplet-shaped NRs before fading away, producing distinct
evolution compared with that in usual two-band NR. When SOC is included, TNPs
would transform into type-II Dirac points while all the NRs have gaped.
Remarkably, the type-II Dirac points inherit the advantages of TNPs: residing
around Fermi energy and exhibiting large linear energy range. Both features
facilitate the observation of interesting phenomena induced by type-II
dispersion. The symmetry protections and low-energy Hamiltonian for the
nontrivial band crossings are discussed.Comment: 7 pages, 5 figures, J. Phys. Chem. Lett. 201
Distinguishing Computer-generated Graphics from Natural Images Based on Sensor Pattern Noise and Deep Learning
Computer-generated graphics (CGs) are images generated by computer software.
The~rapid development of computer graphics technologies has made it easier to
generate photorealistic computer graphics, and these graphics are quite
difficult to distinguish from natural images (NIs) with the naked eye. In this
paper, we propose a method based on sensor pattern noise (SPN) and deep
learning to distinguish CGs from NIs. Before being fed into our convolutional
neural network (CNN)-based model, these images---CGs and NIs---are clipped into
image patches. Furthermore, three high-pass filters (HPFs) are used to remove
low-frequency signals, which represent the image content. These filters are
also used to reveal the residual signal as well as SPN introduced by the
digital camera device. Different from the traditional methods of distinguishing
CGs from NIs, the proposed method utilizes a five-layer CNN to classify the
input image patches. Based on the classification results of the image patches,
we deploy a majority vote scheme to obtain the classification results for the
full-size images. The~experiments have demonstrated that (1) the proposed
method with three HPFs can achieve better results than that with only one HPF
or no HPF and that (2) the proposed method with three HPFs achieves 100\%
accuracy, although the NIs undergo a JPEG compression with a quality factor of
75.Comment: This paper has been published by Sensors. doi:10.3390/s18041296;
Sensors 2018, 18(4), 129
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